Ink jet nozzle arrangement with volumetric ink ejection means
A nozzle arrangement for ejecting ink includes a substrate defining an ink supply passage. A first endless wall extends from the substrate and bounds the ink supply passage. An elongate actuator is operatively anchored at a fixed end to the substrate and at a location external to the confines of the first endless wall. The actuator is configured to be reciprocally bent towards and away from the substrate on receipt of an electrical current. A cover terminates a free end of the actuator. The cover defines a second endless wall which is movably suspended within the confines of the first endless wall so as to define an ink chamber in fluid communication with the ink supply passage. The cover further defines an ink ejection port in fluid communication with the ink chamber through which ink provided into the ink chamber from the ink supply passage can be ejected such that reciprocating movement of the actuator and thus the cover varies a volume of the ink chamber and ejects ink from the ink chamber through the ink ejection port.
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The present application is a continuation of U.S. application Ser. No. 11/015,012 filed on Dec. 20, 2004, which is a continuation of U.S. application Ser. No. 10/893,378 filed on Jul. 19, 2004, now issued as U.S. Pat. No. 6,994,425, which is a continuation of Ser. No. 10/303,347 filed on Nov. 23, 2002, now issued as U.S. Pat. No. 6,767,077, which is a continuation of Ser. No. 09/693,313 filed on Oct. 20, 2000, now issued as U.S. Pat. No. 6,505,916, the entire contents of which are herein incorporated by reference.
FIELD OF THE INVENTIONThis invention relates to an ink jet printhead. More particularly, the invention relates to an ink jet printhead that includes tilt-compensating ink ejection ports.
BACKGROUND TO THE INVENTIONInk jet printheads of the type manufactured using micro-electromechanical systems technology have been proposed in a construction using nozzle chambers formed in layers on the top of a substrate with nozzle chambers formed in the layers. Each chamber is provided with a movable paddle actuated by some form of actuator to force ink in a drop through the nozzle associated with the chamber upon receipt of an electrical signal to the actuator. Such a construction is typified by the disclosure in International Patent Application PCT/AU99/00894 to the Applicant.
The present invention stems from the realisation that there are advantages to be gained by dispensing with the paddles and causing ink drops to be forced from the nozzle by decreasing the size of the nozzle chamber. It has been realised that this can be achieved by causing the actuator to move the nozzle itself downwardly in the chamber thus dispensing with the paddle, simplifying construction and providing an environment which is less prone to the leakage of ink from the nozzle chamber.
Furthermore, Applicant has identified that it would be useful to incorporate a mechanism whereby ink ejection ports could be kept clear of obstructions, such as dried ink or paper dust.
SUMMARY OF THE INVENTIONAccording to a first aspect of the invention, there is provided an ink jet printhead that comprises
a substrate; and
a plurality of micro-electromechanical nozzle arrangements positioned on the substrate, each nozzle arrangement comprising
-
- a nozzle chamber defining structure positioned on the substrate and having a fixed portion that is fast with the substrate and a movable portion that is displaceable with respect to the substrate and that defines an ink ejection port, the movable portion and fixed portion together defining a nozzle chamber and the movable portion being displaceable towards and away from the substrate to reduce and subsequently increase a volume of the nozzle chamber so that ink is ejected from the ink ejection port; and
- an elongate actuator that is anchored to the substrate at one end and operatively engaged with the movable portion at an opposite end, the elongate actuator being bent relative to the substrate on receipt of an electrical signal to displace the movable portion with respect to the fixed portion, wherein
- the ink ejection port is shaped so that tilting of the movable portion results in the ejection of a drop of ink in a direction substantially at right angles to the substrate.
The ink ejection port may be defined by a nozzle rim which has a suitable plan profile to impart said shape to the ink ejection port.
The nozzle rim may be shaped to define a first side which is flatter and broader than an opposite second side, the first side being interposed between the second side and the actuator, such that surface tension effects across the ink ejection port are greater at the second side than at the first side.
The movable portion may include a roof wall and a sidewall depending from a periphery of the roof wall. The fixed portion may include a complementary sidewall. The sidewalls may be configured to overlap when the movable portion is displaced towards the substrate.
The substrate may define a plurality of ink inlet channels. Each ink inlet channel may be in fluid communication with a respective nozzle chamber.
Flow restriction members may be positioned in an opening of each inlet conduit to restrict the flow of ink into the nozzle chamber, thereby to facilitate pressure development in the nozzle chamber as the movable portion is displaced towards the substrate.
According to a second aspect of the invention there is provided an ink jet printhead that comprises
a substrate; and
a plurality of micro-electromechanical nozzle arrangements positioned on the substrate, each nozzle arrangement comprising
-
- a nozzle chamber defining structure having a fixed portion that is fast with the substrate and a movable portion that is displaceable with respect to the substrate and that defines an ink ejection port, the movable portion and fixed portion together defining a nozzle chamber and the movable portion being displaceable towards and away from the substrate to reduce and subsequently increase a volume of the nozzle chamber so that ink is ejected from the ink ejection port; and
- an actuator that is operatively engaged with the movable portion to displace the movable portion with respect to the fixed portion, wherein a projection is positioned on the substrate, the projection being configured so that, when the movable portion is displaced towards the substrate, the projection extends through the ink ejection port.
The substrate may define a plurality of ink conduits, each ink conduit being in fluid communication with a respective nozzle chamber.
The movable portion may include a roof portion and a sidewall depending from a periphery of the roof wall. The fixed portion may include a complementary sidewall, the sidewalls being configured to overlap when the movable portion is displaced towards the substrate.
Each projection may be in the form of a rod-like structure. Each rod-like structure may be mounted on a respective bridge member that spans each ink conduit.
Notwithstanding any other forms that may fall within its scope, one preferred form of the invention will now be described by way of example only with reference to the accompanying drawings in which:
It will be appreciated that a large number of similar nozzles are simultaneously manufactured using MEMS and CMOS technology as described in our co-pending patent applications referred to at the beginning of this specification.
For the purposes of clarity, the construction of an individual ink jet nozzle arrangement will now be described.
Whereas in conventional ink jet construction of the type described in our above referenced co-pending patent applications, ink is ejected from a nozzle chamber by the movement of a paddle within the chamber, according to the present invention the paddle is dispensed with and ink is ejected through an ink ejection port in a movable portion of a nozzle chamber defining structure, which is moved downwardly by a bend actuator, decreasing a volume of the nozzle chamber and causing ink to be ejected from the ink ejection port.
Throughout this specification, the relative terms “upper” and “lower” and similar terms are used with reference to the accompanying drawings and are to be understood to be not in any way restrictive on the orientation of the nozzle arrangement in use.
Referring now to
An ejection port is defined by rim 9 located in the roof portion 6 so as to define an opening for the ejection of ink from the nozzle chamber as will be described further below.
The roof portion 6 and downwardly depending sidewalls 7 are supported by a bend actuator 10 typically made up of layers forming a heated cantilever which is constrained by a non-heated cantilever, so that heating of the heated cantilever causes a differential expansion between the heated cantilever and the non-heated cantilever causing the bend actuator 10 to bend as a result of thermal expansion of the heated cantilever.
A proximal end 11 of the bend actuator 10 is fastened to the substrate 1, and prevented from moving backwards by an anchor member 12 which will be described further below, and the distal end 13 is secured to, and supports, the roof portion 6 and sidewalls 7 of the nozzle arrangement.
In use, ink is supplied to the nozzle chamber through conduit 2 and opening 3 in any suitable manner, but typically as described in our previously referenced co-pending patent applications. When it is desired to eject a drop of ink from the nozzle chamber, an electric current is supplied to the bend actuator 10 causing the actuator to bend to the position shown in
When the electric current is cut off, the actuator 10 reverts to the straight configuration as shown in
In one form of the invention, the opening 3 in floor portion 5 is relatively large compared with the cross-section of the nozzle chamber and the ink droplet is caused to be ejected through the nozzle rim 9 upon downward movement of the roof portion 6 by viscous drag in the sidewalls of the aperture 2, and in the supply conduits leading from the ink reservoir (not shown) to the opening 2. This is a distinction from many previous forms of ink jet nozzles where the “back pressure” in the nozzle chamber which causes the ink to be ejected through the nozzle rim upon actuation, is caused by one or more baffles in the immediate location of the nozzle chamber. This type of construction can be used with a moving nozzle ink jet of the type described above, and will be further described below with specific reference to
In order to prevent ink leaking from the nozzle chamber during actuation i.e. during bending of the bend actuator 10, a fluidic seal is formed between sidewalls 7 and 8 as will now be further described with specific reference to
The ink is retained in the nozzle chamber during relative movement of the roof portion 6 and floor portion 5 by the geometric features of the sidewalls 7 and 8 which ensure that ink is retained within the nozzle chamber by surface tension. To this end, there is provided a very fine gap between downwardly depending sidewall 7 and the mutually facing surface 16 of the upwardly depending sidewall 8. As can be clearly seen in
In order to make provision for any ink which may escape the surface tension restraint due to impurities or other factors which may break the surface tension, the upwardly depending sidewall 8 is provided in the form of an upwardly facing channel having not only the inner surface 16 but a spaced apart parallel outer surface 18 forming a U-shaped channel 19 between the two surfaces. Any ink drops escaping from the surface tension between the surfaces 7 and 16, overflows into the U-shaped channel where it is retained rather than “wicking” across the surface of the nozzle strata. In this manner, a dual wall fluidic seal is formed which is effective in retaining the ink within the moving nozzle mechanism.
As has been previously described in some of our co-pending applications, it is desirable in some situations to clear any impurities which may build up within the nozzle opening and ensure clean and clear ejection of a droplet from the nozzle under actuation. A configuration of the present invention using a projection in combination with a moving nozzle ink jet is shown in the accompanying
As can be seen in
As the roof portion 6 returns to its original position upon straightening of the bend actuator 10 as shown in
It will be appreciated that as the bend actuator 10 is bent causing the roof portion to move downwardly to the position shown in
The correction of this non-perpendicular movement can be achieved by providing the nozzle rim 9 with an asymmetrical shape as can be clearly seen in
By carefully tailoring the shape and characteristics of the nozzle rim 9, it is possible to completely compensate for the tilting of the roof portion 6 during actuation and to propel the ink drop from the nozzle in a direction perpendicular to the floor portion 5.
Although, as described above, the backpressure to the ink held within the nozzle chamber may be provided by viscous drag in the supply conduits, it is also possible to provide a moving nozzle ink jet with backpressure by way of a significant constriction close to the nozzle. This constriction is typically provided in the substrate layers as can be clearly seen in
The bend actuator which is formed from a heated cantilever 28 positioned above a non-heated cantilever 29 joined at the distal end 13 needs to be securely anchored to prevent relative movement between the heated cantilever 28 and the non-heated cantilever 29 at the proximal end 11, while making provision for the supply of electric current into the heated cantilever 28.
The non-heated cantilever 29 is provided with outwardly extending tabs 32 which are located within recesses 33 in the sidewall 31, giving further rigidity, and preventing relative movement between the non-heated cantilever 29 and the heated cantilever 28 in the vicinity of the anchor 27.
In this manner, the proximal end of the bend actuator is securely and firmly anchored and any relative movement between the heated cantilever 28 and the non-heated cantilever 29 is prevented in the vicinity of the anchor. This results in enhanced efficiency of movement of the roof portion 6 of the nozzle arrangement.
Claims
1. A nozzle arrangement for ejecting ink, the nozzle arrangement comprising:
- a substrate defining an ink supply passage;
- a first endless wall extending from the substrate and bounding the ink supply passage;
- an elongate actuator operatively anchored at a fixed end to the substrate and at a location external to the confines of the first endless wall, the actuator being configured to be reciprocally bent towards and away from the substrate on receipt of an electrical current; and
- a cover which terminates a free end of the actuator, the cover defining a second endless wall which is movably suspended within the confines of the first endless wall so as to define an ink chamber in fluid communication with the ink supply passage, the cover further defining an ink ejection port in fluid communication with the ink chamber through which ink provided into the ink chamber from the ink supply passage can be ejected such that reciprocating movement of the actuator and thus the cover varies a volume of the ink chamber and ejects ink from the ink chamber through the ink ejection port.
2. A nozzle arrangement as claimed in claim 1, wherein the first endless wall defines an endless channel to collect ink which passes between the first and second endless walls.
3. A nozzle arrangement as claimed in claim 1, wherein each of the endless walls is hexagonal in shape.
4. A nozzle arrangement as claimed in claim 1, wherein the actuator includes a current delivery arrangement which is electrically coupled to the actuator arm.
5. A nozzle arrangement as claimed in claim 4, wherein the actuator includes a heated cantilever member to which the current delivery arrangement is electrically coupled and which is configured to bend upon heating when current is delivered to it.
6. A nozzle arrangement as claimed in claim 5, wherein the actuator further includes a non-heated cantilever member fast with the heated cantilever member such that the actuator experiences differential thermal expansion and contraction to cause bending.
7. A nozzle arrangement as claimed in claim 4, wherein the current delivery arrangement comprises a drive circuitry layer of the substrate.
8. A nozzle arrangement as claimed in claim 1, further including an endless ledge that is fast with the substrate and extends inwardly with respect to the channel to define a narrowing ink barrier between the ink supply passage and the ink chamber.
9. A nozzle arrangement as claimed in claim 1, further including a support which extends from the substrate and to which the actuating arm is fast, cantilever-fashion.
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Type: Grant
Filed: Oct 11, 2006
Date of Patent: Sep 1, 2009
Patent Publication Number: 20070030308
Assignee: Silverbrook Research Pty Ltd (Balmain, New South Wales)
Inventor: Kia Silverbrook (Balmain)
Primary Examiner: Stephen D Meier
Assistant Examiner: Geoffrey Mruk
Application Number: 11/545,566
International Classification: B41J 2/05 (20060101);